Optical waveguide and method for manufacturing the same

Abstract

The invention provides an optical waveguide including a resin substrate containing an inorganic filler, and at least a UV-absorbing layer, a lower cladding layer, a patterned core layer, and an upper cladding layer laminated above the resin substrate in this order, wherein the core layer has been patterned through light exposure and development, and the UV-absorbing layer has a thickness of 10 to 50 μm, and a method for producing an optical waveguide, including a step of forming a UV-absorbing layer on a resin substrate containing an inorganic filler; a step of forming a lower cladding layer on the UV-absorbing layer; a step of forming a core layer on the lower cladding layer; a step of subjecting the core layer to light exposure to thereby transfer a pattern having a given shape to the core layer; a step of developing the core layer to thereby form a core pattern; and a step of forming an upper cladding layer on the patterned core layer. According to the present invention, an optical waveguide having a high-resolution core pattern can be produced.

The invention claimed is: 
     
       1. An optical waveguide comprising:
 a resin substrate containing an inorganic filler; and 
 at least a UV-absorbing layer, a lower cladding layer, a patterned core layer, and an upper cladding layer laminated above the resin substrate in this order, 
 wherein 
 the lower cladding layer, the patterned core layer, and the upper cladding layer are formed from a resin composition which comprises (i) a base polymer, (ii) a photopolymerizable compound, and (iii) a photopolymerization initiator, 
 the core layer has been patterned through light exposure and development, 
 the UV-absorbing layer has a thickness of 20 to 50 μm, and 
 a content of the inorganic filler is 15 to 65 vol. %. 
 
     
     
       2. The optical waveguide according to  claim 1 , wherein
 the UV-absorbing layer is formed from a photosensitive resin composition, which comprises: 
 (A) a thermoplastic polymer having a carboxyl group, 
 (B) a photopolymerizable compound having a polymerizable ethylenically unsaturated group in the molecule thereof, and 
 (C) a photopolymerization initiator. 
 
     
     
       3. The optical waveguide according to  claim 2 , wherein
 the (B) photopolymerizable compound includes a urethane compound having an ethylenically unsaturated group. 
 
     
     
       4. The optical waveguide according to  claim 3 , wherein
 the urethane compound having an ethylenically unsaturated group is produced through reaction between a urethane compound having an isocyanate group at each end and a hydroxyl-group-having ethylenically unsaturated compound, and 
 the urethane compound having an isocyanate group at each end is produced through reaction between a polycarbonate compound having a hydroxyl group at each end and a diisocyanate compound. 
 
     
     
       5. The optical waveguide according to  claim 1 , wherein
 the UV-absorbing layer has a UV transmittance of 50% or less at a wavelength of the light exposure. 
 
     
     
       6. The optical waveguide according to  claim 1 , wherein
 the inorganic filler is silica. 
 
     
     
       7. A method for producing an optical waveguide, comprising:
 a step of forming a UV-absorbing layer on a resin substrate containing an inorganic filler; 
 a step of forming a lower cladding layer on the UV-absorbing layer; 
 a step of forming a core layer on the lower cladding layer; 
 a step of subjecting the core layer to light exposure to thereby transfer a pattern having a given shape to the core layer; 
 a step of developing the core layer to thereby form a core pattern; and 
 a step of forming an upper cladding layer on the patterned core layer, wherein 
 a lower cladding layer-forming film, a core layer-forming film, and an upper cladding layer-forming film are employed respectively in the steps of forming a lower cladding layer, a core layer, and an upper cladding layer, 
 the UV-absorbing layer has a thickness of 20 to 50 μm, 
 a content of the inorganic filler is 15 to 65 vol. %, and 
 the lower cladding layer-forming film, the core layer-forming film, and the upper cladding layer-forming film are formed from a resin composition which comprises (i) a base polymer, (ii) a photopolymerizable compound, and (iii) a photpolymerization initiator. 
 
     
     
       8. The method for producing an optical waveguide according to  claim 7 , wherein
 the step of forming a UV-absorbing layer comprises laminating a UV-absorbing film on the substrate and pressing the film to the substrate under heating. 
 
     
     
       9. The optical waveguide according to  claim 1 , wherein the resin composition is the same for each of the lower cladding layer, the patterned core layer, and the upper cladding layer. 
     
     
       10. The optical waveguide according to  claim 1 , wherein the resin composition from which the lower cladding layer and the upper cladding layer are formed is different from the resin composition from which the patterned core layer is formed. 
     
     
       11. The method for producing an optical waveguide according to  claim 7 , wherein the resin composition is the same for each of the lower cladding layer-forming film, the core layer-forming film, and the upper cladding layer-forming film. 
     
     
       12. The method for producing an optical waveguide according to  claim 7 , wherein the resin composition from which the lower cladding layer-forming film and the upper cladding layer-forming film are formed is different from resin composition from which the core layer-forming film is formed.